The present invention relates to a metal plate with a bead, more particularly to a metal plate wherein a bead terminates inside the metal plate. The metal plate of the invention can be used solely as a metal plate gasket, or can be combined with other metal plates to form a steel laminate gasket.
In a metal gasket, when a hole is to be sealed, a bead is formed around the hole. When the gasket with the bead is compressed, the bead deforms to provide surface pressure therearound, by which an area around the hole is securely sealed. Also, a bead may be formed on a metal plate as explained hereinafter.
In a gasket for an internal combustion engine, especially a cylinder head gasket, in case a cylinder head is firmly attached to a cylinder block, equal surface pressure may not be formed between the cylinder head and cylinder block. Unbalanced surface pressure is caused by, for example, unequal arrangement of cylinder holes and other holes, or bolts for connecting the cylinder head and cylinder block. Unbalanced surface pressure may happen in case a cylinder head bends relative to a cylinder block by heat in use.
In case unbalanced surface pressure occurs, surface pressure must be balanced. Otherwise, unbalanced surface pressure causes leakage around holes to be sealed.
In case unbalanced surface pressure is formed between a cylinder head and cylinder block, a thin metal plate may be attached to a part of a gasket, or a bead may be formed in a plate at a portion where special support is required. This kind of bead extends at a portion of a gasket and terminates in a middle of a metal plate.
Namely, as shown in FIGS. 1 and 2, a bead 10 terminates in a middle of a plate 11. At an end of the bead 10, side edges 12 converge together, and the height of the bead 10 decreases.
On the other hand, surface pressure obtained by a bead is determined by width and height of the bead in case the same metal plate is used. Namely, as width and height of a bead decrease, surface pressure increases though compressibility decreases. Therefore, in case the side edges 12 converge and the height of the bead decreases as in the conventional bead 10, surface pressure at an end of the bead 10 becomes strong.
This kind of strong surface pressure at an end of a bead causes unbalance of surface pressure, which may cause leakage around holes to be sealed. Namely, in case a bead terminates in a middle of a plate, unbalanced surface pressure occurs, so that fluid inside holes may leak therefrom.
Therefore, one object of the present invention is to provide a metal plate with a bead, in which surface pressure gradually decreases at an end of the bead when the bead is compressed.
Another object of the invention is to provide a metal plate as stated above, which can be easily and economically manufactured.
Further objects and advantages of the invention will be apparent from the following description of the invention.